Conventionally, hemodialysis is performed with a hemodialysis apparatus causing blood and a dialysis solution to flow through a dialyzer. A blood circuit through which blood is caused to flow and a dialysis solution circuit through which the dialysis solution is caused to flow are connected to the dialyzer.
As such a hemodialysis apparatus, one capable of performing an online hemodialysis filtration treatment (hereinafter referred to as on-line HDF (hemodiafiltration)) by supplying a dialysis solution to a blood circuit during dialytic treatment (Patent Literature 1) is known.
In the hemodialysis apparatus performing the on-line HDF, a replacement fluid passage is provided between the blood circuit and the dialysis solution circuit, and a replacement fluid port for connection to the replacement fluid passage is provided for the dialysis solution circuit. This replacement fluid port can be opened and closed by a lid member.
When preparatory operations for hemodialysis treatment are performed, the replacement fluid port is in the closed state, with the replacement fluid passage detached from the replacement fluid port. In this state, a dialysis solution substitution step to fill the dialysis solution circuit with the dialysis solution is performed. The lid member is thereafter removed from the replacement fluid port and the replacement fluid passage is connected to the replacement fluid port.